*7 Hannigan argues that the CHP's procedures for enforcing the helmet law do not violate the Fourth Amendment, or alternatively, that Easyriders did not make the showing necessary to justify the district court's issuing an injunction against the CHP. Easyriders argues that the CHP violated the Fourth Amendment by stopping and citing motorcyclists without regard to whether they had actual knowledge of the helmet's non-compliance with Standard 218, and that motorcyclists stand to suffer irreparable harm if the CHP's method of enforcing the helmet law is not enjoined. "The requirements for the issuance of a permanent injunction are 'the likelihood of substantial and immediate irreparable injury and the inadequacy of remedies at law.' " American-Arab Anti-Discrimination Comm., 70 F.3d at 1066-67 (quoting LaDuke v. Nelson, 762 F.2d 1318, 1322 (9th Cir.1985), modified, 796 F.2d 309 (9th Cir.1986)). [FN5]

Easyriders alleges that its members and the individual plaintiffs stand to suffer irreparable harm due to CHP's policy of stopping and citing motorcyclists without regard to whether the motorcyclists have actual knowledge of their helmet's non-compliance with Standard 218.

We are mindful that the injunction at issue here enjoins the law enforcement activities of a state law enforcement agency. "[I]n reviewing a district court's injunction against an agency of state government, we scrutinize the injunction closely to make sure that the remedy protects the plaintiffs' federal constitutional and statutory rights but does not require more of state officials than is necessary to assure their compliance with federal law." Clark v. Coye, 60 F.3d 600, 604 (9th Cir.1995). This requires both that there be a determination that the conduct of the CHP violates federal constitutional law, id. at 603-04, and that the scope of the injunction is no broader than necessary to provide complete relief to the named plaintiffs and the members of Easyriders. Meinhold v. United States Dep't of Defense, 34 F.3d 1469, 1480 (9th Cir.1994) (reversing nationwide injunction against Navy from discharging any homosexual servicemen where class had not been certified despite upholding relief in favor of named plaintiff).

A. CHP's Stopping of Motorcyclists With Suspicious Helmets.

The CHP must comply with the Fourth Amendment, as applied to the states through the Fourteenth Amendment, when stopping motorcyclists that it suspects are violating the helmet law. Because the Fourth Amendment prohibits only "unreasonable" searches and seizures, the ultimate test of a seizure's reasonableness entails a balancing of the governmental interest which justifies the intrusion and the level of intrusion into the privacy of the individual. Michigan Dept. of State Police v. Sitz, 496 U.S. 444, 448-49, 110 S.Ct. 2481, 2484, 110 L.Ed.2d 412 (1990). In Terry v. Ohio, 392 U.S. 1, 20-21, 88 S.Ct. 1868, 1879, 20 L.Ed.2d 889 (1967), the Supreme Court articulated the level of suspicion required for a police officer to briefly stop and question an individual for investigatory purposes. This court has further elaborated on the level of suspicion required for so-called "Terry stops" of automobiles.

*8 The Fourth Amendment's prohibition of unreasonable searches and seizures extends to the brief investigatory stop of a vehicle. United States v. Brignoni-Ponce, 422 U.S. 873, 878, 95 S.Ct. 2574, 2578-79, 45 L.Ed.2d 607 (1975). An officer may not detain a motorist without a showing of "reasonable suspicion." [United States v. Rodriguez, 976 F.2d 592, 594 (9th Cir.1992), amended 997 F.2d 1306 (9th Cir.1993).] This "objective basis, or 'reasonable suspicion,' must consist of 'specific, articulable facts which, together with objective and reasonable inferences, form the basis for suspecting that the particular person detained is engaged in criminal activity.' " Id. (citations omitted). A "gloss on this rule prohibits reasonable suspicion from being based on broad profiles which cast suspicion on entire categories of people without any individualized suspicion of the particular person to be stopped." United States v. Rodriguez-Sanchez, 23 F.3d 1488, 1492 (9th Cir.1994). United States v. Garcia-Camacho, 53 F.3d 244, 245-46 (9th Cir.1995). See also United States v. Sokolow, 490 U.S. 1, 7, 109 S.Ct. 1581, 1585, 104 L.Ed.2d 1 (1989) (holding that the "Fourth Amendment requires 'some minimal level of objective justification' for making" a Terry stop, which is "considerably less than proof of wrongdoing by a preponderance of the evidence") (quoting INS v. Delgado, 466 U.S. 210, 217, 109 S.Ct. 1581, 1585, 80 L.Ed.2d 247 (1984)). A determination of whether an officer had "reasonable suspicion" of wrongdoing "is not readily reduced to 'a neat set of legal rules.' " United States v. Hernandez-Alvarado, 891 F.2d 1414, 1416 (9th Cir.1989) (quoting Illinois v. Gates, 462 U.S. 213, 232, 103 S.Ct. 2317, 2329, 76 L.Ed.2d 527 (1983)). Rather, the court must consider "the totality of the circumstances surrounding the stop." United States v. Hall, 974 F.2d 1201, 1204 (9th Cir.1992); see also United States v. Franco-Munoz, 952 F.2d 1055, 1057 n. 3 (9th Cir.1991), cert. denied, 509 U.S. 911, 113 S.Ct. 3015, 125 L.Ed.2d 705 (1993); Hernandez-Alvarado, 891 F.2d at 1416. "This includes the 'collective knowledge of the officers involved, and the inferences reached by experienced, trained officers.' " Hall, 974 F.2d at 1204 (quoting United States v. Sharpe, 470 U.S. 675, 682, 105 S.Ct. 1568, 1675, 84 L.Ed.2d 605 (1985)); see also Hernandez-Alvarado, 891 F.2d at 1416 (noting that this experience may not be used to give the officers unbridled discretion in making a stop).

*9 Nothing in the record indicates that there is a CHP pattern or policy of stopping motorcyclists without reasonable suspicion that the motorcyclists are violating the helmet law. It is indicated by photographs and actual helmets in the record that the helmets of the named plaintiffs all have fiberglass shells and cover only the top of the head above the ears. The liner of the helmets is one half inch thick or less, and the helmets are secured around the motorcyclist's chin by nylon straps which thread through two D-rings. Because a Terry stop requires "considerably less than proof of wrongdoing by a preponderance of the evidence," Sokolow, 490 U.S. at 7, 109 S.Ct. at 1585, an officer need not have a particularized suspicion that a motorcyclist has actual knowledge that his helmet does not comply with Standard 218 if other objective evidence, such as the appearance of the helmet, sufficiently supports an investigatory stop. It is possible that the appearance of a helmet alone would be insufficient to support reasonable suspicion that the helmet law was being violated if the helmet law had been very-recently enacted or there had been no publicity regarding certain small helmets' non-compliance with Standard 218. In such a case, it might be unreasonable to draw the inference, based only on the helmet's appearance, that a motorcyclist knows of his helmet's non- compliance. However, given the large amount of publicity about novelty helmets and otherwise non-complying helmets, as indicated by the numerous press releases and motorcycle magazine articles in the record regarding non- conforming helmets, an officer would usually have at least "reasonable suspicion," based on reasonable inferences drawn from the helmet's appearance and publicity regarding non-complying helmets, that the motorcyclist was violating the helmet law.[FN6]

While there are some helmets that are DOT approved that are similar in appearance to non-complying helmets, as demonstrated by the helmets submitted to the court and a CHP brochure designed to help consumers distinguish legal and "novelty" helmets, " 'the facts used to establish "reasonable suspicion" need not be inconsistent with innocence.' " Rodriguez, 976 F.2d at 594 (quoting Franco-Munoz, 952 F.2d at 1057). Thus, an officer may stop a motorcyclist for investigatory purposes based on the appearance of the helmet, even if in many cases the motorcyclist will not have the requisite knowledge of non-compliance and thus will be innocent of wrongdoing. There are no allegations in this case that the CHP has repeatedly stopped motorcyclists wearing helmets that actually comply with Standard 218 or that did not have a physical appearance that merited further investigation. Investigatory stops of motorcyclists with apparently non-complying helmets serve the dual purpose of identifying individuals who are intentionally violating the law, and informing riders who are unknowingly wearing non- complying helmets that their helmets do not comply and possibly will not protect them sufficiently in the case of an accident. Any minimal intrusion imposed upon individuals whose helmets do comply with helmet laws is justified by the furtherance of these important government goals, and the underlying California policy goal of providing "an additional safety benefit" to its motorcyclist citizens. See Cal. Veh.Code s 27803(f) (West Supp.1995). There is no showing in the record that the initial stopping of the motorcyclists violated the Fourth Amendment.

*10 Of course, investigatory stops that initially comply with the Fourth Amendment because they are supported by reasonable suspicion may violate the Fourth Amendment if they continue for a period of time beyond that which is necessary for brief investigation. Terry stops are "constitutionally permissible only where the means utilized are the least intrusive reasonably available. '[A]n investigative detention must be temporary and last no longer than is necessary to effectuate the purpose of the stop.' " Kraus v. County of Pierce, 793 F.2d 1105, 1108 (9th Cir.1986) (quoting Florida v. Royer, 460 U.S. 491, 500, 103 S.Ct. 1319, 1325, 75 L.Ed.2d 229 (1983)), cert. denied, 480 U.S. 932, 107 S.Ct. 1571, 94 L.Ed.2d 763 (1987). If the investigatory stops of motorcyclists continued for an extended period of time, probable cause that the motorcyclists knew about the helmet's non-compliance could be required. "Obviously, if an investigative stop continues indefinitely, at some point it can no longer be justified as an investigative stop. But [Supreme Court] cases impose no rigid time limitation on Terry stops." Sharpe, 470 U.S. at 685, 105 S.Ct. at 1575. See also Allen v. City of Los Angeles, 66 F.3d 1052, 1056 (9th Cir.1995) (holding that an initially lawful Terry stop can be converted into a full-fledged arrest for which probable cause is required, but noting that there is "no bright line rule for determining when an investigatory stop crosses the line and becomes an arrest") (citation omitted). However, the possibility that police officers will exceed the permissible period of detention for Terry stops without probable cause cannot salvage the first half of the injunction, which imposes a more substantial burden on the CHP than is required to protect motorcyclists' constitutional rights.